Various communication and radar systems operate in Ku bands or higher radio frequency (RF) bands. In these systems, an RF power has to be monitored to immediately compensate a communication condition change, such as an atmospheric pressure change, an interference, a displacement or a direction change. To do so, an RF power detector is employed in an RF power stage to adjust an RF gain or signal level according to a detection result. However, due to circuit limitation, the detection result has a deviation. Therefore, the industry focuses on enhancing preciseness of the detection result.